For next generation automotive radar applications (e.g., 77 GHz long-range radar and 79 GHz short-range radar applications) and very high data rate communications about a 5 GHz VCO tuning range over a temperature operation range of −40 to 125° C. is required. An additional 3.5 GHz should be added in the VCO designs to compensate the VCO frequency temperature drift and also to assure a high production yield. Therefore the VCO should have a total electrically tuning range of about 8.5 GHz with also fulfilling the very challenging phase noise request. Moreover, a VCO tuning voltage range of 0.3 to 2.8 V is required due to the low cost request by using only one 3.3 V supply voltage.
Actual VCO architectures cannot meet this 5 GHz tuning range over complete temperature range with the required phase noise specification. Some work-around is under discussion or investigation. An idea is to have two or even more VCO designs in one chip. However, this idea will require more chip area and also needs a complex algorithm to choose one of the different VCO operations during system running. Another idea is to use a switchable capacitance to select the VCO frequency bands. However, this idea will degrade the VCO continuous tuning range (maybe not be able to meet the large electrical tuning range request for short range radar application) and will also degrade the VCO phase noise.